/*
 * Copyright � 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using Spring.Core.IO;
using Spring.Util;

namespace Spring.Objects.Factory.Config;

/// <summary>
/// Implementation of <see cref="IVariableSource"/> that
/// resolves variable name against Java-style property file.
/// </summary>
/// <seealso cref="Properties"/>
/// <author>Aleksandar Seovic</author>
[Serializable]
public class PropertyFileVariableSource : IVariableSource
{
    private IResource[] locations;
    protected Properties properties;
    private readonly object objectMonitor = new object();
    private bool ignoreMissingResources;

    /// <summary>
    /// Gets or sets the locations of the property files
    /// to read properties from.
    /// </summary>
    /// <value>
    /// The locations of the property files
    /// to read properties from.
    /// </value>
    public IResource[] Locations
    {
        get { return locations; }
        set { locations = value; }
    }

    /// <summary>
    /// Convinience property. Gets or sets a single location
    /// to read properties from.
    /// </summary>
    /// <value>
    /// A location to read properties from.
    /// </value>
    public IResource Location
    {
        set { locations = new IResource[] { value }; }
    }

    /// <summary>
    /// Sets a value indicating whether to ignore resource locations that do not exist.  This will call
    /// the <see cref="IResource"/> Exists property.
    /// </summary>
    /// <value>
    /// 	<c>true</c> if one should ignore missing resources; otherwise, <c>false</c>.
    /// </value>
    public bool IgnoreMissingResources
    {
        set { ignoreMissingResources = value; }
    }

    /// <summary>
    /// Before requesting a variable resolution, a client should
    /// ask, whether the source can resolve a particular variable name.
    /// </summary>
    /// <param name="name">the name of the variable to resolve</param>
    /// <returns><c>true</c> if the variable can be resolved, <c>false</c> otherwise</returns>
    public bool CanResolveVariable(string name)
    {
        lock (objectMonitor)
        {
            if (properties == null)
            {
                properties = new Properties();
                InitProperties();
            }

            return properties.Contains(name);
        }
    }

    /// <summary>
    /// Resolves variable value for the specified variable name.
    /// </summary>
    /// <param name="name">
    /// The name of the variable to resolve.
    /// </param>
    /// <returns>
    /// The variable value if able to resolve, <c>null</c> otherwise.
    /// </returns>
    public string ResolveVariable(string name)
    {
        lock (objectMonitor)
        {
            if (properties == null)
            {
                properties = new Properties();
                InitProperties();
            }

            return properties.GetProperty(name);
        }
    }

    /// <summary>
    /// Initializes properties based on the specified
    /// property file locations.
    /// </summary>
    protected virtual void InitProperties()
    {
        foreach (IResource location in locations)
        {
            bool exists = location.Exists;
            if (!exists && ignoreMissingResources)
            {
                continue;
            }

            using (Stream input = location.InputStream)
            {
                properties.Load(input);
            }
        }
    }
}
